Conventional switching power supplies often include a way to monitor an amount of current delivered to a respective load. The amount of delivered current can be monitored for any number of reasons such as telemetry, load-line control, current consumption tracking, to increase conversion efficiency, etc.
Several methods have been used to measure current delivered by a respective power supply to a load. For example, Hall effect sensors can be implemented to measure magnetic field and calculate a respective current. Unfortunately, Hall effect sensors are expensive and cannot be integrated into respective semiconductor device.
Other conventional designs include adding a respective resistor in a current source path of the power supply. A voltage monitor circuit measures current passing through the added resistor to identify how much current is delivered to a respective load. This method is undesirable because the added resistor consumes power that does not power the load.
Another method is known as DCR (DC Resistance). This method includes utilizing the resistance of a respective inductor through which current flows to calculate the amount of current delivered to a respective load. This method is undesirable because it cannot be integrated in a semiconductor device; it requires trimming of a respective gain circuit; it requires temperature compensation, etc.
Additional methods include current mirroring techniques and measuring the voltage across a respective synchronous field effect transistor in a power supply. Both of these methods are undesirable. For example, current mirroring requires complex circuitry and high-bandwidth amplifier circuitry. The conventional method of measuring the voltage across a respective drain-source of a synchronous field effect transistor requires a complex and highly robust circuit because the voltage at switch node (junction node of control switch, synchronous switch, and inductor) is susceptible to transient voltages through a switching cycle.